1. Field
The present invention relates to a cooling device having a heat-radiating portion for radiating heat from a heat-generating component and a fan for applying cooling air to the heat radiating portion, and to an electronic apparatus, such as a portable computer, which incorporates this cooling device.
2. Description of the Related Art
A CPU is incorporated in electronic apparatuses such as portable computers. The heat that a CPU generates while operating increases as its data-processing speed rises or as it performs more and more functions. The higher the temperature of the CPU, the less efficiently the CPU operates or the more likely it may fail to operate.
Any electronic apparatus comprising a CPU that generates much heat while operating incorporates a cooling device that cools the CPU. The cooling device is provided in the housing of the electronic apparatus, along with the other major components of the apparatus, such as the wiring board and the hard disk drive.
The conventional cooling device has a heat receiving portion, a heat radiating portion, a heat pipe, and a fan. The heat receiving portion is thermally coupled to a CPU. The heat radiating portion radiates is spaced apart from the heat receiving portion and radiates heat from the CPU. The heat pipe transfers the heat of the CPU to the heat radiating portion. The fan has an air outlet port, through which cooling air is supplied to the heat radiating portion.
In the conventional cooling device, the heat of the CPU is transferred from the heat receiving portion through the heat pipe to the heat radiating portion. The heat radiating portion is cooled with the cooling air applied from the fan. The heat of the CPU, transferred to the heat radiating portion, is released from the housing by virtue of heat exchange with the cooling air. The ambient temperature of the CPU is thereby maintained at such a value that the CPU operates well.
The heat pipe mechanically connects the heat receiving portion and the heat radiating portion. Thus, the heat receiving portion, heat radiating portion and heat pipe constitute one module. The module is held on the wiring board, on which the heat receiving portion is provided, with the CPU mounted on it. The fan is fastened, with screws, to the inner surface of the housing, with its air outlet port opposed to the heat radiating portion. The fan and heat radiating portion are located side by side, away from the heat receiving portion.
In the conventional cooling device, the position of the heat radiating portion is determined by that of the heat receiving portion that is held on the wiring board. By contrast, the position of the fan is determined by that of the inner surface of the housing. In other words, their positions depend on the positions of different components, which are likely to change. Their positions inevitably differ from the desired ones. In some cases, a large gap develops between the heat radiating portion and the fan, and the cooling air flowing toward the heat radiating portion inevitably leaks through this gap.
A cooling device is known, which has a duct that extends to the air outlet port of a fan to prevent the leakage of cooling air. In this cooling device, the duct surrounds the heat radiating portion, thereby preventing the cooling air from leaking through the gap between the heat radiating portion and the air outlet port of the fan. Jpn. Pat. Appln. KOKAI Publication 2003-101272, for example, discloses an electronic apparatus that has a cooling device of this type.
In the cooling device disclosed in the above-identified Japanese publication, the heat pipe connects the heat receiving portion to the heat radiating portion that is surrounded by the duct. The duct has through holes that guide the heat pipe. These holes have a far larger diameter than the heat pipe, in order to compensate for the changes in position of the fan and heat radiating portion. Inevitably, a gap develops between the heat pipe and the rim of each through hole.
Consequently, the cooling air coming from the fan leaks through the gap. The cooling air is applied to the heat radiating portion in a smaller amount than otherwise. The heat radiating portion cannot be efficiently cooled. Ultimately, the CPU may not be cooled sufficiently.